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mcgarrett · 06-02-2020, 10:17 AM

Could be one of three things going on:
1). As has been noted - disconnect the cable, clean and lube it. Also make sure the it is sound and without damage at the ends.

2). The "turtle" speedometer drive bolted to the drive shaft that drives the cable could be running dry and worn out the gear. Remove the 2 bolts that hold it to the driveshaft and check that all the teeth are good, has plenty of grease, and spins freely.

3). If your speedometer is in original condition and has never been touched, could be that the drive mechanism (speedo head) needs to be lubed with a light oil. You will need to remove the speedo from the car, but don't have to take it apart. Looking on the back side of the mechanism itself, there is a tiny brass plug pressed into the cast pot metal housing of the speedo drive head that can be pried out with a small jewelers screwdriver and some patience. Gently work it our of its hole. Behind that little plug is a felt wick that is designed to hold light oil to keep the little shafts and gears lubricated. (3-in-1 household oil or sewing machine oil will work fine.) Make sure that felt wick is saturated with oil and gently press the little brass plug back in the hole and reassemble. I've done this procedure many times on old, dry speedos that operated erratically and they smoothed out and worked like brand new again.

06-02-2020, 10:17 AM	#4
mcgarrett Senior Member Join Date: Dec 2013 Location: Waxahachie, Texas Posts: 949	Re: 1936 speedometer bouncing wildly Could be one of three things going on: 1). As has been noted - disconnect the cable, clean and lube it. Also make sure the it is sound and without damage at the ends. 2). The "turtle" speedometer drive bolted to the drive shaft that drives the cable could be running dry and worn out the gear. Remove the 2 bolts that hold it to the driveshaft and check that all the teeth are good, has plenty of grease, and spins freely. 3). If your speedometer is in original condition and has never been touched, could be that the drive mechanism (speedo head) needs to be lubed with a light oil. You will need to remove the speedo from the car, but don't have to take it apart. Looking on the back side of the mechanism itself, there is a tiny brass plug pressed into the cast pot metal housing of the speedo drive head that can be pried out with a small jewelers screwdriver and some patience. Gently work it our of its hole. Behind that little plug is a felt wick that is designed to hold light oil to keep the little shafts and gears lubricated. (3-in-1 household oil or sewing machine oil will work fine.) Make sure that felt wick is saturated with oil and gently press the little brass plug back in the hole and reassemble. I've done this procedure many times on old, dry speedos that operated erratically and they smoothed out and worked like brand new again.